class TreeNode(object):
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right


class Solution(object):
    def inorderTraversal(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
        def bianli(root):
            if not root:
                bianli(root.left)
                out.append(root.val)
                bianli(root.right)
        out = []
        bianli(root)
        return out



